Appendix 2 part 3F (Category D) is for cash savings ONLY
You would need to have £62,500 in cash savings to follow this route only.
Additionally the full amount of £62,500 must have been held for at least 6 months.

Please do read and fully understand the requirements.

The actual VALUES of shares etc are not allowable.
It's only the INCOME from those shares that count.

Be cautious.

Concerning the National Insurance number, you need only input that if there is a question asking for it.
Appendix 2 part 3F does NOT ask for (or require) a National Insurance number

Do you have the intention to complete either Appendix 2 part 3D (Category C) or Appendix 2 part 3E (Category E) or perhaps even both ?

On those parts of the form you do not need to complete, just leave blank.

No offence intended, just trying to help